Apparatus for handling parts

ABSTRACT

This invention is addressed to a new and improved apparatus for handling heavy metal parts, such as displacement of the part through a blast zone in which the parts are subjected to surface treatment including a rotating tunnel adapted to receive parts in sliding engagement therethrough and a reciprocating drawbar having projections thereon adapted to be displaced toward the tunnel for engagement of the projections with parts in the tunnel and adapted to be displaced away from the tunnel for disengagement of the projections from the parts in the tunnel during reciprocation of the drawbar whereby parts are advanced through the tunnel in a spaced relation by the projections on the reciprocating drawbar.

Noble [451 I Apr. 24,1973 '7 APPARATUS FOR HANDLING PARTS [75] Inventor: Myron C. Noble, South Bend, Ind.

[73] Assignee: Wheelabrator-Frye Inc., New York,

NrY.

[22] Filed: Feb. 2, 1971 [21] Appl. No.: 111,914

52 U.S. Cl ..51/15' [51] Int. Cl. ..B24c 3/08, B24c 9/00 [58] Field ofSearch ..51/l5, 14, 8,9

[56] References Cited UNITED STATES PATENTS 2,204,636 6/1940 Turnbull ..5 H14 X 2,565,341 8/1951 Arispe ..5l/l5 2,918,071 12/1959 Umbricht et al. 134/144 3,517,465 6/1970 Freeman et aL... ....5l/15 X 3,534,504 10/1970 Carpenter ..5l/l5 3,626,641 12/1971 Powell ..5l/9 X Primary Examiner-Donald G. Kelly Attorney-McDougall, Hersh & Scott This invention is addressed to a new and improved apparatus for handling heavy metal parts, such as displacement of the part through a blast zone in which the parts are subjected to surface treatment including a rotating tunnel adapted to receive parts in sliding engagement therethrough and a reciprocating drawbar having projections thereon adapted to be displaced toward the tunnel for engagement of the projections with parts in the tunnel and adapted to be displaced away from the tunnel for disengagement of the projections from the parts in the tunnel during reciprocation of the drawbar whereby parts are advanced through the tunnel in a spaced relation by the projections on the reciprocating drawbar.

ABSTRACT 20 Claims, 1 1 Drawing Figures Patented April 24, 1973 4 Sheets-Sheet 1 INVENTOE Patented April 24, 1973 4 Sheets-Sheet 2 1 I I l I I E IIHHIIII Patented April 24, 1973 4 Sheets-Sheet 3 cux Q Patented April 24, 1973 4 Sheets-Sheet 4 m ii' APPARATUS FOR HANDLING PARTS This invention relates to the surface treatment of heavy metal parts, and more particularly to a new and improved method and apparatus for the continuous movement of heavy metal parts from a source of supply to a delivery station with intermediate exposure of substantially all of the surfaces of the parts to blast media for surface treatment thereof.

In US. Pat. No. 3,517,465, description is made of a method and apparatus for the surface treatment of heavy metal objects or parts in which use is made of a plurality of open cages supported on their ends on ring members to enable the cages to be continuously rotated. The cages are cycled to a loading'station at which the parts are inserted into the cages, and the loaded cages are displaced onto the leading end of a roller conveyor. The roller conveyor is formed of a pair of laterally spaced turning rolls which extend continuously through an enclosed blast zone having one or more centrifugal throwing wheels for projecting particulate material at high speeds onto the loaded cages as they are advanced along the roller conveyor from the inlet end through the blast cabinet to the outlet end of the conveyor.

The rolls of the conveyor are turned continuously to cause the loaded cages to continuously rotate as they are advanced along the conveyor through the blast cabinet whereby maximum surface exposure of the metal parts to the particulate blast material is realized.

As described in the above patent, the loaded cages are advanced along the conveyor through the blast cabinet by incremental displacement of each loaded cage as it is deposited on the loading end of the conveyor to thereby align the cages in an end-to-end relationship for advancement through the blast cabinet in a single column. Beyond the blast cabinet, the loaded cages are displaced to an unloading station at which the surface-treated parts are removed from the cage, and the empty cage is returned by another conveyor to the inlet end for reloading and use in another cycle of operation.

While the method and apparatus described in the aforementioned patent represents a significant advance in the art and facilitates continuous operation in the treatment of heavy metal parts at relatively high speeds and with uniformity of surface treatment, such operations nevertheless include the relatively complex steps of loading and unloading the cages as well as the recycle of the empty cages for reuse. Such steps involve the use of additional equipment and floor space, and thus contribute undesirably to the overall cost of the operation.

Further improvements in the art of surface treating of heavy metal parts have been achieved with the apparatus disclosed and claimed in copending application ofJames W. Fogle et a]. Ser. No. 568,299, filed July 27, 1966, and entitled Machine and Method for Surface Treatment of Large Articles" and assigned to the same assignee as is this application. As described in this copending application, use is made ofa single elongate open cage which extends continuously through the blast zone through which the parts to be surface treated are advanced in an end-to-end relation of the entrance to the exit instead ofa plurality of separate short cages as employed in the above-mentioned patent. The elonequal to the rotational speed of the cage whereby the rotating part can be displaced into the rotating cage by means of, for example, a pneumatic or hydraulic ram. Thus, the parts in the cage are advanced therethrough by displacing a part into the cage which in turn causes each of the parts to be advanced since the parts are aligned in an abutting end-to-end relationship.

While the method and apparatus of the copending application represents a distinct improvement over the cage device of the above patent in that it avoids the necessity of loading and unloading separate cages and recycling the cages for reuse, the ram-cage machine nevertheless suffers from numerous disadvantages. Since the parts in the tunnel are in an abutting, end-toend relation as described, there is no space between the parts to permit the particulate blast material to contact the ends of the parts. In addition, since the parts are advanced through the tunnel by one part pushing, it is necessary that the parts have relatively flat ends. Even with relatively flat ends, the condition of one part pushing on another can cause jamming or wedging in the tunnel. Moreover, because of the mode by which the parts are advanced through the tunnel, the apparatus of the above-identified application is incapable of emptying itself.

It is accordingly an object of the present invention to provide a new and improved apparatus for use in the surface treatment of heavy parts which overcomes the foregoing disadvantages of the cage and ram-cage machines described above.

It is a further object of the invention to provide a new and improved apparatus for use in the surface treatment of heavy parts in which the parts are advanced through a rotating cage in a spaced relation to permit exposure of the ends of the parts to particulate blast material and in which the pushing of one part on another is completely avoided. 7

It is a more specific object of the invention to provide a new and improved apparatus for use in the surface treatment of heavy parts in which the use of separate cages which must be loaded, unloaded and recycled is completely avoided.

These and other objects and advantages of the invention will appear more fully hereinafter, and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in which:

FIG. 1 is a side elevation view of the preferred form of the apparatus of this invention;

FIG. 2 is a sectional view taken along the lines 2--2 in FIG. 1;

FIG. 3 is a sectional view taken along the lines 33 in FIG. 1;

FIG. 4 is a plan view of the embodiments shown in FIGS. 1 to 3;

FIG. 5 is an enlarged view of one of the apparatus shown in FIGS. 1 to 4;

F IG. 6 is a sectional view taken along the lines 66 in FIG.

FIG. 7 is a side elevation view of another embodiment of apparatus embodying the features of this invention;

FIG. 8 is a sectional view taken along the lines 8-8 in FIG. 7;

FIG. 9 is a sectional view taken along the lines 9-9 in FIG. 7;

FIG. 10 is a sectional view taken along the lines 10- 10 in FIG. 7; and

FIG. 11 is a view of another guide mechanism embodying the features of this invention.

The concepts of the present invention reside in a new and improved parts handling system for indexing parts through a rotatable blast tunnel of the type described in the aforementioned copending application including a drawbar having a plurality of tooth-like projections thereon adapted to engage a surface of each of the parts in the tunnel mounted for reciprocating movement and a cam assembly which serves to move the drawbar to a position in which the projections engage the parts in the tunnel during the forward stroke of the drawbar to advance each of the parts through the tunnel in a spaced relationship and then to move the drawbar to a position in which the projections on the drawbar are disengaged from the parts during the return stroke of the drawbar whereby the drawbar is thereafter in a position to repeat the cycle of operation.

The tooth-like projections are spaced along the drawbar by distances slightly greater than the lengths of the parts in the tunnel, with one projection being associated with each part in the tunnel. Thus, the projections on the drawbar serve to push the parts through the tunnel and serve to maintain the parts in the desired spaced relationship. In this way, the individual parts at no time push'upon adjacent parts, and access of the particulate blast media to the ends of the parts is facilitated.

Referring now to the drawings for a more detailed description of the invention, there is shown in FIGS. 1, 2 and 4 the preferred embodiment of the invention including a tunnel 10 of the type described in the aforementioned copending application which extends through a blast zone defined by generally cylindrical walls 12 shown in broken lines and end walls 14 and 16. As can best be seen in FIG. 2, the tunnel 10 in this embodiment is defined by a plurality of spaced support bars 18, 20, 22, 24, 26 and 28 arranged to form a tunnel having a cross section corresponding to the cross section of the parts to be advanced therethrough. As is described in the copending application, the tunnel 10 is dimensioned to receive the pans to be processed in sliding engagement therethrough. In the most preferred form, the support bars 18, 20, 22, 24, 26 and 2a are formed with rounded surfaces 29, 30, 32, 34, 36 and 38, respectively, in contact with the surfaces of the parts to minimize the surface area of the tunnel in surface contact with the parts and insure that maximum surface area of the parts is accessible to the blast media.

Circular end walls 14 and 16 are formed with openings therethrough in communication with the tunnel 10, including opening 40 in end wall 16 in FIG. 2 to enable the parts to be fed to the tunnel through the III opening in wall 14 and from the tunnel through opening 40 in wall 16. End walls 14 and 16 are mounted for rotation by way of, for example, rollers .42 and 44, respectively, and the bars 18, 20, 22, 24, 26 and 28 are fixed to the end walls 14 and 16 to be rotatable therewith. Thus, as the blast zone is rotated, the tunnel is similarly rotated to expose the parts therein to the blast media supplied from conventional blasting wheels or the like means provided as described in the aforementioned copending application, but not illustrated in the drawings for the sake of simplicity.

At the left end of tunnel 10, there is provided means 46 for continuously feeding parts to the tunnel 10 as the latter is continuously rotated. The details of the feed means 46 form no part of the present invention and are fully described in the aforementioned copending application. As described therein, the feed means 46 impart to the parts to be fed to tunnel 10 a rotary motion and bring the parts to a rotary speed which is substantially the same as the speed of the rotating tunnel to enable the parts to be advanced into the tunnel 10 as hereinafter described.

At the right end of the tunnel, there is provided a discharge zone 48 from which the parts advanced through the tunnel are discharged by means of the type described in the aforementioned copending application. As set forth in this copending application, the

discharge means (not illustrated in the drawing)' operate in a similar manner as the feed means and rotate the pans at a speed substantially the same as that of the tunnel 10 to enable the parts to be discharged from the rotating tunnel.

The parts are advanced through tunnel 10 by means of a drawbar 50 which extends longitudinally over the entire length of tunnel 110 through slots or openings 54 and 56 in end walls 14 and 16, respectively, and is provided with a plurality of tooth-like projections 52 adapted to engage a surface of the parts in the tunnel 10 to push the parts through tunnel l0. Drawbar 50 is mounted for longitudinal reciprocation by means of cam rollers 58 and 60 at the left and right ends thereof, respectively, which are carried by legs 62 and 64, respectively.

As is best shown in FIGS. 1, 5 and 6, cam rollers 58 and 60 are mounted in follower or guide plates 66 and 68 rotatably mounted on frames '70 and 72. In the preferred form and as best illustrated in FIG. 6, use is made of a pair of guide plates 68 with the leg 64, having a pair of opposing rollers on each face thereof, mounted between the spaced guide plates. In the embodiment shown in these figures frames 70 and 72 are mounted for rotation on rollers 69 and 71, respectively, with tunnel It), and thus drawbar 50 is similarly rotatable with tunnel 10.

Follower plates 66 and 68 are formed with a series of slots therein which serve to control and guide the movement of drawbar 50 and hence the projections 52 relative to tunnel 10. As shown in FIGS. 1 and 5, each of the follower plates is formed with a pair of parallel, spaced horizontal slots 74 and 76, and a pair of spaced inclined n'ser slots 78 and 80. Together these slots define a path for the cam rollers 58 and 68 formed by the edges of a parallelogram. As will be appreciated by those skilled in the art, as the drawbar 50 is reciprocated, cam roller 58 is displaced through the slot 74, and the drawbar 50 is advanced in the forward direction as shown by the arrow in the drawing. Accordingly, the projections 52 on drawbar 50 extend into tunnel and are advanced therethrough in the same direction to engage and advance parts in the tunnel 10 during the forward stroke. For example, projection 52' engages a surface of a part in the feed zone to advance that part into the tunnel. Parts in the tunnel are each advanced therethrough by a distance corresponding to the length of the forward stroke of the drawbar as limited by the length of slot 74 by a corresponding projection. In this way, only the projections serve to advance the parts in the tunnel, and the pushing of one part on another is completely avoided. To this end, the projections 52 on drawbar 50 are spaced each from the other by a distance only slightly greater than the longitudinal dimension of the parts processed through the tunnel.

As the cam roller 58 reaches the forward end of the slot 74, it is raised upwardly and rearwardly by passage through rearwardly inclined slot 80, thereby raising drawbar 50 to withdraw and disengage projections 52 from the parts in the tunnel 10. The drawbar 50 is then displaced rearwardly as cam roller 58 is advanced through slot 76, and is simultaneously maintained in the raised position in which the projections are withdrawn or disengaged from the parts in the tunnel, in the return stroke of draw bar 50. At the end of travel through slot 76, the cam roller 58 travels downwardly and forwardly through forwardly inclined slot 78 to thereby lower the drawbar 50 and cause projections 52 to engage a preceding part in tunnel 10 for repetition of the cycle of operation. Thus, it will be seen from the foregoing that the configuration of the slotted guide member allows the projections on the drawbar to be brought up behind the part, allowing for a certain amount of float of the parts in the machine when they are not in contact with the drawbar tooth.

While the foregoing description has been made with reference to the rearward cam rollers 58, it will be understood that the forward cam rollers 60 are displaced through substantially similar paths to maintain the drawbar 50 substantially horizontal during reciprocation. It will also be understood that the parallelogram path defined by thefollower plates is subject to considerable variation in terms of the configuration of the path followed by the cam rollers, so long as the drawbar is displaced relative to the tunnel by a distance to permit the projections to become disengaged from the parts in the tunnel during the return stroke of the drawbar.

The drawbar can be reciprocated by a number of means. In accordance with the preferred embodiment of the invention, use is made of a scotch yoke mechanism to convert the rotary motion of the tunnel and drawbar to a reciprocatory motion as shown in FIGS. 1, 3, 5 and 6 of the drawings. As shown in these figures, the assembly of the tunnel 10, the drawbar 50 and supports 70 are mounted to rotate together about a longitudinal axis. The apparatus is driven by suitable means such as a motor 79 connected to one end of the apparatus by a chain drive 81 or the like.

The opposite end of the apparatus is provided with a rotatable frame fixed to frame 72 to be rotatable therewith, and including a pair of spaced circular plates 82 and connected each to the other by connecting bars 86. Plates 82 and 84 are rotatably mounted by means of rollers 71 and 85. As is best shown in FIGS. 1 and 3, a carriage 88 is mounted for longitudinal displacement along connecting bars by means of rollers 90. As illustrated in FIG. 3, the connecting bars have a generally square cross section, and each pair of rollers 90 are in contact with two adjacent faces of the connecting bars to maintain the rollers 90 in contact with bars 88 during rotation of carriage 88 with frame 72.

Pivotally attached to the carriage 88 by means of pin 92 is the yoke 91 of :1 scotch yoke assembly 94, the details of which are Well-known to those skilled in the art and form no part of the present invention. The input shaft 96 to the scotch yoke 94 is fixed to ground at 98, preferably by means of a shear pin (not illustrated in the drawing) to avoid damage to the machine in the unlikely event that parts in the machine should cause the machine to jam. Thus, as the tunnel and drawbar are rotated, the scotch yoke 94 is similarly rotated since the carriage is mounted for rotation with the frames 72 and connecting bars 86. However, the shaft 96 is fixed, and thus the rotation of the yoke actuates the scotch yoke mechanism to thereby cause the carriage 88 to reciprocate along connecting bars 86.

The carriage 88 is also connected to drawbar 50 by means of a tie rod 100. Therefore, as the carriage 88 is reciprocated by the scotch yoke 94, the drawbar 50 is caused to reciprocate in response to reciprocation of carriage 88 and thus in response to rotation of the tunnel and drawbar. The gear ratio of the scotch yoke gear box can be varied in accordance with the particular application. For example, use can be made of a gear ratio of 1:1 which provides one revolution of the gear box and hence one complete cycle of reciprocation of the drawbar per revolution of the tunnel.

One of the advantages of the scotch yoke assembly as the actuating means for the drawbar is that the drawbar is reciprocated with constant accelerationthrough the first half of each stroke and constant deceleration through the last half of each stroke, thereby providing excellent control of the parts in the tunnel.

Thus, in the operation of the device of this embodiment of the invention, the tunnel, the drawbar and associated support suspensions including the reciprocating carriage 88 are rotated, and parts are continuously supplied to the tunnel through feed means 46. The reciprocation of the drawbar 50 causes parts fed to the tunnel to be advanced into the tunnel by means of the projections on the drawbar; while in the tunnel, the parts which are continuously rotated in the tunnel are subjected to a barrage of treating particulate matter for the surface treatment of the parts. Thereafter, the parts are discharged from the tunnel through the discharge zone 48. One of the primary advantages of this particular embodiment of this invention, as indicated above, is that the drawbar is actuated to displace the parts through the tunnel in response to the rotation of the drawbar and tunnel, thereby providing excellent synchronization between the rotation of the tunnel and the advancement of the parts therethrough.

Another embodiment of the invention is illustrated in FIGS. 7 to 10 of the drawings in which the drawbar for advancing parts through the tunnel is reciprocated by different means. In this embodiment, the tunnel 102 extends through the blast zone 104. As shown in FIG. 9, the tunnel can be defined by a plurality of support bars 18', 20, 22, 24, 26' and 28 formed with desired rounded surfaces 29, 30, 32', 34, 36 and 38', respectively, and arranged to define an open tunnel having the desired cross section. However, it will be understood that the tunnel of this embodiment and for the embodiment shown in FIG. 1 can be defined by a plurality of radially inwardly extending bars as described in the aforementioned copending application.

The tunnel 102 is rotatably mounted in generally the same manner as that described in FIG. 1. The drawbar 106 extends longitudinally through end walls 14' and 16' adjacent to the tunnel, and is rotatable therewith. Drawbar 106 is provided with a plurality of tooth-like projections 1 08 adapted to engage a surface of the parts in the tunnel upon actuation of the drawbar 106.

The drawbar 106 is carried by a pair of follower plates 110 which are similar to those shown in FIG. 1, and define a path for travel by cam rollers 112 which guides the reciprocation of the drawbar. One end of drawbar 106 is connected by way of a connecting rod 114 to a reciprocating piston 118 of a cylinder 116, which may be a hydraulic or pneumatic cylinder. Thus, the drawbar 106 is actuated in response to actuation of the piston 1 18.

- The displacement of the drawbar 106 toward the tunnel to a position in which the projections 108 engage parts in the tunnel is controlled in this embodiment by opposing bias means 120 and 122 near the ends of the drawbar 106 which constantly urge the drawbar 106 toward a position in which the projections 108 are in engagement with the parts in tunnel 102 and a position in which the projections 108 are disengaged from parts in tunnel 102, respectively. For this purpose and as shown in FIG. 10 of the drawing use is made ofa guide roller or the like 124 mounted on a shaft 126. The guide roller is biased against one surface of the drawbar 106 by means of spring 128.

Thus, as the piston and cylinder displace the drawbar 106 forwardly in the direction shownby the arrow in the drawing to advance the parts through the tunnel on the forwardstroke, the cam roller 1 12 travels forwardly through slot 76'. On reaching the end of this slot, the bias roller assembly 122 displaces the drawbar downwardly such that cam roller 112 passes through slot 78' to slot 74, and the cylinder displaces the drawbar 106 rearwardly whereby projections 108 are disen gaged from parts in tunnel 102 and the cam roller passes through slot 74 during the return stroke. As the cam roller 112 reaches the rearward end of this slot, the biased roller assembly 120 raises the drawbar 106 as cam roller 1 12 is passed through slot 80', thereby engaging projections 108 with parts in tunnel 102 for the forward stroke in which the parts are advanced through the tunnel.

In the operation of this embodiment of the invention, parts are continuously supplied to the tunnel 102 through feed zone 127 in the same manner as described in reference to the embodiment shown in FIG. 1, and the tunnel 102 is-continuously rotated. The cylinder 116 is actuated thereby setting drawbar 106 in motion to advance the parts through the continuously rotating tunnel 102 in which they are exposed to blast media. The finished parts are then removed from the apbination with the embodiment illustrated in FIG. 1 of the drawing, although it should be understood that the guide mechanism of this figure can also be used with the apparatus as described in FIG. 7 of the drawings.

As illustrated in FIG. 11 of the drawing, the guide plate 130 is formed with a pair of substantially parallel, spaced horizontal elongate slots 132 and 134 separated each from the other by an intermediate guide member 136. At the rearward end of the intermediate guide member 136, there is provided an arm 138 pivotally mounted at its end 140 and resiliently biased or constantly urged toward the slot 134 to form a cam gate, that is toward the slot which guides the drawbar rearwardly during the return stroke. Similarly, the forward end of the intermediate guide bar is provided with an arm 142 forming a cam gate pivotally mounted about its end and resiliently biased or constantly urged in the opposite direction toward slot 132, that is the slot which guides the drawbar forwardly during the forward stroke during which the parts are advanced through the tunnel. Both arms 138 and 142 are normally in contact with the edges of their slots 134 and 132, respectively, and abut impact pads 146 and 148, respectively, in their unloaded positions shown in the drawing. Similarly, impact pads 154 and 156 may likewise be provided for the arms or cam gates during activation as hereinafter described.

Thus, as the drawbar 50' is reciprocated, the cam roller 60' is displaced rearwardly, through slot 134, during which the projections on thedrawbar are disengaged from parts in the tunnel for the return stroke. As the roller 60' reaches the end of the guide member 136, it rolls onto the arm 138 whereby the weight of the drawbar assembly opposes the action of the bias means (such as spring bias means which are not illustrated in the drawing). However, as roller 60 continues. to roll rearwardly onto arm 138, the leverage of the weight of the drawbar increases and overcomes the bias means whereby the arm 138 is caused to be pivoted downwardly wherebyv roller 60' is advanced onto surface 149 at the rear of slot 134. As will be appreciated by those skilled in the art as the roller 60 is advanced over the arm 138 onto an elevated surface 149 defined by an edge of the lower slot 132 as extended, the arm 138 returns to the starting position shown in FIG. 11, and rolls over surface 149 and down the downwardly sloping edge of slot 132 to enter lot 132 for the forward stroke.

During the forward stroke, the roller 60' is advanced forwardly through slot 132 until reaching the end of the intermediate guide member whereby the forward movement of the roller 60' opposes andovercomes the means urging arm 142 toward slot 132 and advances'to the rear portion 152 of slot 132. As soon as roller 60 passes into the portion 152 of slot 132, arm 142 returns to its rest position as shown and forms an incline for elevation of roller 60' to slot 134 for repetition of the cycle.

One of the advantages of this guide plate mechanism of the invention is that the action of the biased arms as described above facilitates the control of the cam rollers to provide the desired raising and lowering of the drawbar for engagement and disengagement of the projections on the drawbar with parts in the tunnel. While description has been made of the construction and operation of the guide mechanism for one end of the drawbar, it will be understood that the mechanism on the opposite end of the drawbar is generally the same and operates in generally the same manner. I

It will be understood that various changes and modifications can be made in the details of construction, operation and use without departing from the spirit of the invention, especially as defined in the following claims I claim:

1. Apparatus for conveying parts through a tunnel in a spaced relation comprising a rotatable elongated tunnel having open sides adapted to receive parts, means for rotating said tunnel, a drawbar mounted for reciprocation extending longitudinally over the length of said tunnel and having spaced projections rigidly mounted thereon adapted to engage parts in the tunnel, means for reciprocating the drawbar and means for displacing the drawbar in a first direction toward the centerline of the tunnel for engagement of the projections with parts in the tunnel during a forward stroke of the drawbar to advance the parts through the tunnel in a spaced relation and for displacing the drawbar in a second direction away from the centerline of the tunnel for disengagement of the projections from the parts in the tunnel on the return stroke of the drawbar.

2. Apparatus as defined in claim 1 wherein the tunnel and drawbar are mounted for rotation each with the other about a longitudinal axis.

3. Apparatus as defined in claim 1 wherein the means for displacing the drawbar toward and away from the centerline of the tunnel includes a slotted guide means and a cam roller in the slotted guide means connected to the drawbar.

4. Apparatus as defined in claim 3 wherein the slotted guide member includes a pair of horizontally spaced slots, one of which guides the cam roller during the forward stroke of the drawbar with the projections on the drawbar in engagement with parts in the tunnel and the other of which guides the cam roller during the rearward stroke of the drawbar with the projections disengaged from parts in the tunnel.

5. Apparatus as defined in claim 4 wherein the slotted guide member also includes a pair of laterally spaced, inclined slots in communication with the horizontal slots, one of which guides the cam roller at the completion of the forward stroke to displace the drawbar away from the tunnel to disengage the projections from parts in the tunnel and the other of which guides the cam roller at the completion of the rearward stroke to displace the drawbar toward the tunnel for engagement of the projections on the drawbar with parts in the tunnel.

6. Apparatus as defined in claim 4 wherein the horizontally spaced slots are separated each from the other by an elongate, intermediate guide member, the ends of which are provided with cam gate means to control displacement of the projections to and from ongagement with parts in the tunnels.

iii

7. Apparatus as defined in claim 6 wherein the cam gate means include a pair of arms pivotally mounted at one end at each end of the intermediate guide member, one of which is positioned at the rearward end of the guide member and is constantly urged toward the slot which guides the cam roller during the forward stroke and one of which is positioned at the forward end of the guide member and is constantly urged toward the slot which guides the cam roller during the rearward stroke.

8. Apparatus as defined in claim ll wherein the means for reciprocating the drawbar includes a reciprocating carriage assembly mounted for rotation with the tunnel connected to the drawbar, and a scotch yoke assembly having an input shaft and a yoke, with the input shaft being fixed and the yoke being pivotally connected to the carriage whereby rotation of the tunnel carriage actuates the scotch yoke assembly to cause reciprocation of the carriage and drawbar.

9. Apparatus as defined in claim 1 wherein the means for reciprocating the drawbar include a fluid-actuated piston and cylinder.

10. Apparatus as defined in claim 1 which includes means for supplying parts to the tunnel and means for discharging parts from the tunnel.

11. in an apparatus for the surface treatment of large articles including a rotatable elongated tunnel having open sides extending through a blasting housing, the improvement comprising a drawbar mounted for reciprocation extending longitudinally over the length of said tunnel and having spaced projections rigidly mounted thereon adapted to engage parts in the tunnel, means for reciprocating the drawbar and means for displacing the drawbar in a first direction toward the centerline of the tunnel for engagement of the projections with parts in the tunnel during a forward stroke of the drawbar to advance the parts through the tunnel in a spaced relation and for displacing the drawbar in a second direction away from the centerline of the tunnel for disengagement of the projections from the parts in the tunnel on the return stroke of the drawbar.

12. Apparatus as defined in claim 11 wherein the tunnel and drawbar are mounted for rotation each with the other about a longitudinal axis.

13. Apparatus as defined in claim 11 wherein the means for displacing the drawbar toward and away from the centerline of the tunnel includes a slotted guide means and a cam roller in the slotted guide means connected to the drawbarv 14. Apparatus as defined in claim 13 wherein the slotted guide member includes a pair of horizontally spaced slots, one of which guides the cam roller during the forward stroke of the drawbar with the projections on the drawbar in engagement with parts in the tunnel and the other oi which guides the cam roller during the rearward stroke of the drawbar with the projections disengaged from parts in the tunnel.

15. Apparatus as defined in claim 14 wherein the slotted guide member also includes a pair of laterally spaced, inclined slots in communication with the horizontal slots, one of which guides the cam roller at the completion of the forward stroke to displace the drawbar away from the tunnel to disengage the projections from parts in the tunnel and the other of which guides the cam roller at the completion of the rearward stroke to displace the drawbar toward the tunnel for engagement of the projections on the drawbar with parts in the tunnel.

16. Apparatus as defined in claim 14 wherein the horizontally spaced slots are separated each from the other by an elongate, intermediate guide member, the ends of which are provided with cam gate means to control displacement of the projections to and from engagement with parts in the tunnels.

17. Apparatus as defined in claim 6 wherein the cam gate means include a pair of arms pivotally mounted at one end at each end of the intermediate guide member, one of which is positioned at the rearward end of the guide member and is constantly urged toward the slot which guides the cam' roller during the forward stroke and one of which is positioned at the forward end of the guide member and is constantly urged toward the slot which guides the cam roller during the rearward stroke.

18. Apparatus as defined in claim 11 wherein the means for reciprocating the drawbar includes a reciprocating carriage assembly mounted for rotation with the tunnel connected to the drawbar, and a scotch- 

1. Apparatus for conveying parts through a tunnel in a spaced relation comprising a rotatable elongated tunnel having open sides adapted to receive parts, means for rotating said tunnel, a drawbar mounted for reciprocation extending longitudinally over the length of said tunnel and having spaced projections rigidly mounted thereon adapted to engage parts in the tunnel, means for reciprocating the drawbar and means for displacing the drawbar in a first direction toward the centerline of the tunnel for engagement of the projections with parts in the tunnel during a forward stroke of the drawbar to advance the parts through the tunnel in a spaced relation and for displacing the drawbar in a second direction away from the centerline of the tunnel for disengagement of the projections from the parts in the tunnel on the return stroke of the drawbar.
 2. Apparatus as defined in claim 1 wherein the tunnel and drawbar are mounted for rotation each with the other about a longitudinal axis.
 3. Apparatus as defined in claim 1 wherein the means for displacing the drawbar toward and away from the centerline of the tunnel includes a slotted guide means and a cam roller in the slotted guide means connected to the drawbar.
 4. Apparatus as defined in claim 3 wherein the slotted guide member includes a pair of horizontally spaced slots, one of which guides the cam roller during the forward stroke of the drawbar with the projections on the drawbar in engagement with parts in the tunnel and the other of which guides the cam roller during the rearward stroke of the drawbar with the projections disengaged from parts in the tunnel.
 5. Apparatus as defined in claim 4 wherein the slotted guide member also includes a pair of laterally spaced, inclined slots in communication with the horizontal slots, one of which guides the cam roller at the completion of the forward stroke to displace the drawbar away from the tunnel to disengage the projections from parts in the tunnel and the other of which guides the cam roller at the completion of the rearward stroke to displace the drawbar toward the tunnel for engagement of the projections on the drawbar with parts in the tunnel.
 6. Apparatus as defined in claim 4 wherein the horizontally spaced slots are separated each from the other by an elongate, intermediate guide member, the ends of which are provided with cam gate means to control displacement of the projections to and from engagement with parts in the tunnels.
 7. Apparatus as defined in claim 6 wherein the cam gate means include a pair of arms pivotally mounted at one end at each end of the intermediate guide member, one of which is positioned at the rearward end of the guide member and is constantly urged toward the slot which guides the cam roller during the forward stroke and one of which is positioned at the forward end of the guide member and is constantly urged toward the slot which guides the cam roller during the rearward stroke.
 8. Apparatus as defined in claim 1 wherein the means for reciprocating the drawbar includes a reciprocating carriage assembly mounted for rotation with the tunnel connected to the drawbar, and a scotch yoke assembly having an input shaft and a yoke, with the input shaft bEing fixed and the yoke being pivotally connected to the carriage whereby rotation of the tunnel carriage actuates the scotch yoke assembly to cause reciprocation of the carriage and drawbar.
 9. Apparatus as defined in claim 1 wherein the means for reciprocating the drawbar include a fluid-actuated piston and cylinder.
 10. Apparatus as defined in claim 1 which includes means for supplying parts to the tunnel and means for discharging parts from the tunnel.
 11. In an apparatus for the surface treatment of large articles including a rotatable elongated tunnel having open sides extending through a blasting housing, the improvement comprising a drawbar mounted for reciprocation extending longitudinally over the length of said tunnel and having spaced projections rigidly mounted thereon adapted to engage parts in the tunnel, means for reciprocating the drawbar and means for displacing the drawbar in a first direction toward the centerline of the tunnel for engagement of the projections with parts in the tunnel during a forward stroke of the drawbar to advance the parts through the tunnel in a spaced relation and for displacing the drawbar in a second direction away from the centerline of the tunnel for disengagement of the projections from the parts in the tunnel on the return stroke of the drawbar.
 12. Apparatus as defined in claim 11 wherein the tunnel and drawbar are mounted for rotation each with the other about a longitudinal axis.
 13. Apparatus as defined in claim 11 wherein the means for displacing the drawbar toward and away from the centerline of the tunnel includes a slotted guide means and a cam roller in the slotted guide means connected to the drawbar.
 14. Apparatus as defined in claim 13 wherein the slotted guide member includes a pair of horizontally spaced slots, one of which guides the cam roller during the forward stroke of the drawbar with the projections on the drawbar in engagement with parts in the tunnel and the other of which guides the cam roller during the rearward stroke of the drawbar with the projections disengaged from parts in the tunnel.
 15. Apparatus as defined in claim 14 wherein the slotted guide member also includes a pair of laterally spaced, inclined slots in communication with the horizontal slots, one of which guides the cam roller at the completion of the forward stroke to displace the drawbar away from the tunnel to disengage the projections from parts in the tunnel and the other of which guides the cam roller at the completion of the rearward stroke to displace the drawbar toward the tunnel for engagement of the projections on the drawbar with parts in the tunnel.
 16. Apparatus as defined in claim 14 wherein the horizontally spaced slots are separated each from the other by an elongate, intermediate guide member, the ends of which are provided with cam gate means to control displacement of the projections to and from engagement with parts in the tunnels.
 17. Apparatus as defined in claim 6 wherein the cam gate means include a pair of arms pivotally mounted at one end at each end of the intermediate guide member, one of which is positioned at the rearward end of the guide member and is constantly urged toward the slot which guides the cam roller during the forward stroke and one of which is positioned at the forward end of the guide member and is constantly urged toward the slot which guides the cam roller during the rearward stroke.
 18. Apparatus as defined in claim 11 wherein the means for reciprocating the drawbar includes a reciprocating carriage assembly mounted for rotation with the tunnel connected to the drawbar, and a scotch yoke assembly having an input shaft and a yoke, with the input shaft being fixed and the yoke being pivotally connected to the carriage whereby rotation of the tunnel carriage actuates the scotch yoke assembly to cause reciprocation of the carriage and drawbar.
 19. Apparatus as defined in claim 11 wherein the means for reciprocating the drawbar include a fluid-actuated piston And cylinder.
 20. Apparatus as defined in claim 11 which includes means for supplying parts to the tunnel and means for discharging parts from the tunnel. 